Field of the Invention
The present invention relates to a gas leak detection device of gas insulation electric equipment which detects a very small leakage of insulating gas sealed in an airtight container such as a gas insulation switching device, and a gas leak detection method (inspection method) thereof.
Background Art
A gas insulation switching device is a facility which cuts off current instantly in order to protect facilities of an electric power substation, in a case in which abnormal current such as a lightning strike flows. The gas insulation switching device has a structure in which a plurality of gas pressure containers are connected, and a breaker or a disconnecting switch is housed within the gas pressure containers with inert gas. As insulating gas sealed in the gas pressure containers, inert gas is used. As the inert gas, sulfur hexafluoride gas (hereinafter, abbreviate to SF6) is generally used. SF6 is a subject to be managed because the global warming potential is 24,000 times more than CO2, and gas insulation electric equipment including the gas insulation switching device needs to detect a gas leak.
A technology relating to detection of a gas leak of the related art is disclosed in JP-A-2010-193616 (PTL 1). This document focuses on that gas pressure is slowly changed following a change of an external temperature (refer to paragraph 0013 and FIG. 3), and a method of obtaining a conversion pressure converted at a predetermined temperature, by providing temperature sensors that are provided on the outside of the gas pressure containers, and using a temperature value (external temperature) measured at an arbitrary timing and a pressure value (gas pressure) measured when a predetermined delay time has elapsed from the timing (refer to abstract).
In addition, a technology relating to detection of a gas leak of the related art is disclosed in JP-A-2011-130581 (PTL 2). In this document, a gas pressure monitoring device is disclosed in which a conversion pressure inside the airtight container is accurately obtained and is capable of early detection of a gas leak, by removing an influence of uncertain temperature differences inside and outside the airtight container (gas pressure containers), from an inclination of a characteristic curve constituted of transitions in time series of a pressure value and a temperature value measured at a predetermined timing defined to a 24 hour circle (refer to abstract). Further, the document discloses that temperatures inside and outside the airtight container are measured, a characteristic curve obtained by combining a pressure value and a temperature value (any one of an internal temperature and an external temperature of the airtight container) measured at a timing when a difference between two temperatures is small is used, and an inclination of a characteristic curve having high reproducibility is obtained (refer to paragraph 0022).